Signaling system



March 15, 1938. w. H. EDWARDS SIGNALING SYSTEM Filed May 1, 1935 INVENTOR WHZ'dwalcds ATTORNEY Lil Patented Mar. 15, 1938 UNITED STATES PATENT OFFBQE SIGNALING SYSTEM Application May 1, 1935, Serial No. 19,294

1 Claim.

This invention relates to signaling systems and more particularly to arrangements for providing a plurality of signaling lines with individual visual signals and a common audible signal.

The arrangements of the invention are particularly adapted for signaling systems adapted to be utilized with telephone lines. It has often been found desirable in telephone systems, for example at .an exchange or in a room where a plurality of lines terminate, to provide each of the lines with a common audible signal and individual visual signals. It is one of the primary objects of the arrangements of this invention to provide a means for furnishing a service of this type. In the arrangements of the invention this is accomplished by providing each line with a gas-filled discharge tube adapted to be operated in response to the signaling current transmitted over the line and which when operated will provide a visual signal individual to that line. All of the gasfilled discharge tubes would be connected to a common signaling circuit and the operation of any one of the tubes would cause the operation of a common audible signal therein. Other objects and features of the invention will appear more fully from the detailed description thereof hereinafter given.

The invention may be more fully understood from the following description, together with the accompanying drawing, in the figure of which is shown a circuit diagram embodying a preferred form of the invention.

In the drawing are shown three signal lines such as L1, L2, and L3. At the distant end of these lines are shown means for applying thereto signaling currents. For example, the key I might be used to apply alternating signaling current from the source I to the line L1; the key K2 might be used to apply to the line L2, alternating signaling current of the type known as A. C.-D. C. in which a battery I is connected between the alternating current source and ground; and the key K3 might be used to apply signaling current from the source 3 to the line L3. Obviously other arrangements for applying signaling currents to the lines might be utilized. At the other end of each line there would be provided a gas-filled discharge tube. For example, there would be connected in the line L1 a gas-filled discharge tube 4 in series with a condenser l; in the line L2 there would be connected a gas-filled tube 5 in series with .a condenser 8; and in the line L3 there would be connected a gas-filled tube 6 in series with the condenser 9. The gas-filled tubes utilized are shown as of the type commonly referred to in the art as a cold cathode ionic tube of the double-gap type. Such tubes usually possess a cathode, coated preferably with some material to reduce the cathode fall, or activated, as this is termed, an auxiliary electrode, also activated and so spaced from the cathode that the breakdown voltage between this electrode and the cathode is relatively low. In the tube 4 the cathode is designated H and the auxiliary electrode is designated iii. The discharge path between the cathode and auxiliary electrode is spoken of as the control discharge path, or control gap. Tubes of this type are also provided with an anode, which has been designated It, so spaced from the cathode that the breakdown voltage therebetween is much greater than that from cathode to auxiliary electrode. The minimum voltage to sustain a discharge, once started, will be nearly the same for the two discharge paths, the main gap, or anode to cathode path being possibly 10 volts higher. In this type of tube it is found that if a voltage less than the breakdown, but above the sustaining voltage, is applied to the main gap, namely between cathode and anode, and a discharge is caused to pass through the control gap, a breakdown of the main gap will take place, being triggered oil by the control gap. Accordingly, when signaling current is applied to any of the lines such, for example, as. the line Li a discharge will take place across the control gap, namely, between electrodes ill and H, and this will cause a discharge to pass across the main gap, namely, between electrodes ii and i2. The discharge across the control gap will be in the nature of a luminous discharge but will be slight in view of the current limiting condenser, but the discharge across the main gap will be large and will serve as an individual visual signal for the line L1. The discharge across the main gap will cause signaling current to be transmitted over the common conductor l3 to the common signaling apparatus i l, shown for purposes of illustration as a ringer but which of course could be a relay, lamp or other apparatus. This Will cause operation of the ringer M. In a like manner, signaling current applied to either of the other lines such as L2 or L3 will cause the operation of the tube 5 or 6. Their operation will give an individual visual signal for each line and will also cause the operation of the common audible signal M.

It has been found that if the anodes of all of the tubes were connected directly to the common signal, the illumination of the individual tubes when signaling current was being sent over several of the lines simultaneously could not be depended upon, because if the voltage of the ringing current transmitted over the line first operated was equal to or higher than. the voltage supply on another line, the voltage drop caused in the common circuit by the first applied ringing voltage would prevent tubes on the circuits from breaking down or obtaining enough current to illuminate properly. Accordingly, the arrangements of this invention avoid this diffidrawing-schematically as Z1, Z2, and Z3.

individual impedance elementsare shown in the These impedance elements, however, may be either an inductance, capacity or resistance, or a combination of them. A capacity may be preferable since it tends to resonate with the inductance of EL1,EL2=Instantaneous voltages of ringing current supply of lines L1 and L2 ER=Instantaneous voltage across ringer I 4 Es=Sustaining voltage of main gap of discharge tubes of 4 and 5 EB=Breakdown voltage of main gap of discharge tubes 4 and 5 Ex=Voltage available to breakdown tube 4 Then, since ES=EB-10 volts, the conditions when ringing on L2 are EL2=ER+ES neglecting line drop.

If EL1=EL2, then if Em is applied after Em EX=EL2-ER OI Es Consequently EX is insufficient to break down the tube 4 as it is 10 volts below the required voltage.

However, if the impedances Z1 and Z2 are introduced, the voltages across these will be EZl and E22.

Then while ringing on L2,

If ringing is applied to L1, and Em is equal to ELZ the voltage available before breakdown on the main gap of tube 4 is:

-.culty by :providing in the individual anode circult of 'each tube an impedance element. 'These Assuniing'Ezzis greater than I0 volts, or'20av0lts EX=Es+20 volts or sufiicient to break {down and maintain tube it.

If for "any reason a. signal other than that provided by the luminous :discharge is desired that is individual to each line, the impedances shown would take the form of relays, audible signals, lamps or other arrangements without interfering with the common ringing signal or the luminous discharges from the tubes.

Although a grounded return path for the ringing current through the common signal is shown, a metallic path could of course be used.

While the arrangements of the invention have been disclosed as embodied in certain specific forms which are deemed desirable, it is understood they are capable of embodiment in many and other Widely varied forms without departing from the spirit of the invention as defined by the appended claim.

What is claimed is:

A telephone signaling system comprising a plurality of lines, means for applying telephone signaling current to each of said lines, a gasfilled discharge tube of the cold cathode double gap type connected to each of said lines, each of said tubes having two electrodes which form a control gap adapted to be discharged when signaling current is applied to the line and an anode electrode which together with one of said other electrodes forms a main gap adapted to be discharged and to give a luminous discharge when said control gap is discharged, a signaling circuit common to all of said lines, means for connecting said common signaling circuit to the anodes of each of said tubes whereby it will be operated when any of said tubes are discharged solely by said telephone signaling currents applied to said line, and individual impedance devices connected between each of said anodes and said common signaling circuit.

WILLIAM HOPPLE EDWARDS. 

